1. Amphotericin B lipid complex, a new formulation by E. R. Squibb Inc., was found to be well tolerated by normal volunteers but provided five fold lower blood levels than the commercial formulation and caused transient asymptomatic liver function abnormalities in 2 of 8 persons. 2. The polymerase chain reaction can detect as little Candida albicans DNA as that in a single fungal cell; the test may be useful diagnostically. 3. Gamma interferon therapy of patients with chronic granulomatous disease increased the ability of the patient's neutrophils to damage Aspergillus hyphae, suggesting that the therapy may improve host defense against aspergillosis. 4. Polyclonal antibody was raised in rabbits against a 69 Kd human monocyte protein. This is thought to be the surface protein that facilitates host defense by binding Aspergillus spores to monocytes and macrophages.